11655551561 has 2 divisors, whose sum is σ = 11655551562. Its totient is φ = 11655551560.

The previous prime is 11655551519. The next prime is 11655551597. The reversal of 11655551561 is 16515555611.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10109095936 + 1546455625 = 100544^2 + 39325^2 .

It is a cyclic number.

It is not a de Polignac number, because 11655551561 - 2³⁰ = 10581809737 is a prime.

It is a super-2 number, since 2×11655551561² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (11655553561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5827775780 + 5827775781.

It is an arithmetic number, because the mean of its divisors is an integer number (5827775781).

Almost surely, 2^11655551561 is an apocalyptic number.

It is an amenable number.

11655551561 is a deficient number, since it is larger than the sum of its proper divisors (1).

11655551561 is an equidigital number, since it uses as much as digits as its factorization.

11655551561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 112500, while the sum is 41.

The spelling of 11655551561 in words is "eleven billion, six hundred fifty-five million, five hundred fifty-one thousand, five hundred sixty-one".